Simultaneous sample purification, enrichment and analysis of pharmaceuticals, illicit drugs, pollutants, biotechnological products, synthetic organic reaction products and food/flavor ingredients from complex matrices can be performed using porous hollow fiber or porous-disk liquid-membrane devices. The devices are part of a multi-well (e.g. 96-well) plate. The devices can be used for selective separation and enrichment of complex mixtures containing trace levels of analytes, and can be used in tandem with analytical instruments which routinely handle multiple samples under high throughput screening conditions. A multi-well/multi-vial plate can into state-of-the-art HPLC or GC sampling systems or LC/MS or GC/MS instruments. Samples can be enriched several orders of magnitude and can directly be withdrawn from the fiber and injected into the chromatographic instruments. Alternatively, these enriched samples can be introduced directly into MS, CE or other detection devices. Selective extraction of complex mixtures of analytes can be achieved through variation of acceptor phase chemistry, liquid membrane coating, pore size control of the hollow fibers, nature of the polymer from which the hollow fibers are made or pH of the acceptor phase.